Space skipping for multi-dimensional image rendering

A graphics processing unit comprising:

• a ray-casting engine arranged to form a two-dimensional image by computing rays extending from a camera location, through the two-dimensional image and into a three dimensional volume, jittering the ray start position by up to one voxel in the direction of the ray in order to mitigate wood grain artifacts using a pre-computed jitter texture, and carrying out integration along those rays;
• a space skipping logic arranged to clip rays computed by the ray-casting engine;
• the ray-casting engine being arranged such that integration is only performed along the clipped rays;
• and
• the space skipping logic being arranged to reduce the resolution of the volume data to form a volume pyramid having at least one smaller, lower-resolution volume and to use the volume pyramid to clip the rays and to terminate a ray when a brick satisfying an opacity condition is encountered, the at least one smaller, lower-resolution volume being a proxy volume, each proxy volume storing minimum and maximum opacity values for the next higher volume.

One or more tangible device-readable media with device-executable instructions that, when executed by a graphics processing unit, direct the graphics processing unit to perform steps comprising:

• carrying out ray-casting to form a two-dimensional image by computing rays extending from a camera location, through the two-dimensional image and into a three dimensional medical volume, and carrying out integration along those rays;
• jittering the ray start position by UP to one voxel in the direction of the ray in order to mitigate wood grain artifacts using a pre-computed jitter texture:
• clipping the rays;
• controlling the ray-casting such that integration is only performed along the clipped rays;
• reducing the resolution of the three dimensional medical volume to form a volume pyramid having at least one smaller, lower-resolution volume and using the volume pyramid to clip the rays, the at least one smaller, lower-resolution volume being a proxy volume, each proxy volume storing minimum and maximum opacity values for the next higher volume;
• and
• terminating a ray when a brick satisfying an opacity condition is encountered.